The present invention is concerned with a warp knitting machine having (a) a weft thread magazine with at least two transport arrangements which move the weft threads towards the needles, (b) weft thread forwarding means which individually deliver the weft threads onto the rear side of the needle bed and (c) a transport assistance arrangement which comprises, at least one support element having a support surface for the weft threads, extending in the forwarding direction.
It has been found that in warp knitting machines of large working breadth, it is not possible to maintain the tension in the weft threads, which run from one forwarding means over the entire machine breadth to another forwarding means, at a sufficient level that the weft threads do not sag in the middle. This danger of sag is particularly serious with heavy threads or with threads of high elasticity. If a weft thread sags, however, there is no way to insure that it will be securely grasped by the weft thread forwarding means and brought to the rear of the needle bed.
In warp knitting machine of the Prior Art (DE-PS 24 32 252) the sagging is prevented by means of support elements which are formed either by the upper side of a conical winding spindle or by the underside of a conical winding spindle working together with a wire frame. In both cases the weft threads are transported to the knitting needles in the rotating notches of the winding spindle. This turning drive adds considerably to the capital cost of the machine furthermore, in order to introduce the weft threads into the winding slots an additional set of slotted wheels is required.
If one does not provide rigid support during the forward transportation of the weft threads, a more or less large degree of friction arises between the weft threads and the support surfaces during the weft thread transportation step which is dependent upon the nature of the upper surface of the thread. This friction operates as a braking force on weft threads so that the weft threads in the middle section of the machine trail with respect to the thread segments proximate to the two transport arrangement at the edges of the machine. This braking force raises the thread tension to the point that the tension overrides the braking force and the threads snap forward in an uncontrolled manner. Since this occurs differently with individual threads and in an uncontrolled manner, the resultant thread distribution brings about a substantial change in the thread spacing particularly in the middle segment between the two transport arrangements so that inconsistencies arise in the placement of the weft threads.
The purpose of the invention is to provide a warp knitting machine of the prior art which insures a trouble free provision of the threads to the thread forwarding means at a lower mechanical cost.